import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;

public class Test1 {
    public static void main(String[] args) {
        int[][] arr = {{5,6},{1,2},{3,4}} ;
        Arrays.sort(arr , (int[]a1 ,int[]a2)->{
          return  a1[0]- a2[0] ;
        });
      
    }
}
